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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Anatomical terms of location | 1/5 | https://en.wikipedia.org/wiki/Anatomical_terms_of_location | reference | science, encyclopedia | 2026-05-05T07:26:06.044970+00:00 | kb-cron |
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and axes. The meaning of terms that are used can change depending on whether a vertebrate is a biped or a quadruped, due to the difference in the neuraxis, or if an invertebrate is a non-bilaterian. A non-bilaterian has no anterior or posterior surface for example but can still have a descriptor used such as proximal or distal in relation to a body part that is nearest to, or furthest from its middle. International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. For example, Terminologia Anatomica, Terminologia Neuroanatomica, and Terminologia Embryologica for humans and Nomina Anatomica Veterinaria for animals. These allow parties that use anatomical terms, such as anatomists, veterinarians, and medical doctors, to have a standard set of terms to communicate clearly the position of a structure.
== Introduction ==
Standard anatomical terms of location have been developed, usually based on Latin and Greek words, to enable all biological and medical scientists, veterinarians, medical doctors and anatomists to precisely delineate and communicate information about animal bodies and their organs, even though the meaning of some of the terms often is context-sensitive. Much of this information has been standardised in internationally agreed vocabularies for humans (Terminologia Anatomica, Terminologia Neuroanatomica, and Terminologia Embryologica), with Nomina Anatomica Veterinaria and Nomina Embryologica Veterinaria used for animal anatomy. Different terms are used for those vertebrates that are bipedal and those that are quadrupedal. The reasoning is that the neuraxis, and therefore the standard anatomical position is different between the two groups. Unique terms are also used to describe invertebrates, because of their wider variety of shapes and symmetries.
=== Standard anatomical position ===
Because animals can change orientation with respect to their environment, and because appendages like limbs and tentacles can change position with respect to the main body, terms to describe position need to refer to an animal when it is in its standard anatomical position, even when its appendages are in another position. This helps to avoid confusion in terminology when referring to the same animal in different postures. In humans, this refers to the body in a standing position with arms at the side and palms facing forward. In quadrupeds this is an animal standing upright with all four feet on the ground and the head facing forward. For a fish this is belly down with neutral appendages.
=== Planes ===
Anatomical terms describe structures with relation to three main anatomical planes. Anatomical planes are useful in a number of fields including medical imaging, embryology, and the study of movement. The three main plane orientations are:
The sagittal planes, also called the parasagittal planes or paramedian planes, are planes that divide the body into left and right. The central one of these is the median plane, also called the midsagittal plane, which passes through the head, spinal cord, navel and, in many animals, the tail. The coronal plane or frontal plane divides the body into front and back parts. In quadrupeds this plane is termed the dorsal plane and divides the body into dorsal (towards the backbone) and ventral (towards the belly) parts. The transverse plane, also called the axial plane or horizontal plane, is perpendicular to the other two planes. Sagittal planes and transverse planes are used as anatomical lines to delineate bodily regions. There are several transverse planes with clinical relevance in the division of the torso into sections. They include the transpyloric plane, the subcostal plane, and the transumbilical plane.
=== Axes ===
The three axes of a vertebrate, are formed in embryonic development before and during the gastrulation stage. Distinct ends of the embryo are chosen, and the axis is named according to those directions. The three main axes of a bilaterally symmetrical animal that intersect at right angles, are the left-right, the craniocaudal, and the anteroposterior axes.
The left-right axis, also known as the horizontal or frontal axis The craniocaudal axis, also known as the rostrocaudal, longitudinal or cephalocaudal The anteroposterior axis, also known as the dorsoventral, or sagittal axis An organism that is round, or asymmetrical may have different axes.
== Main terms ==
=== Superior and inferior === In the standard human anatomical position, superior (from Latin super 'above') or cranial, describes something that is nearer to the head, and inferior (from Latin inferus 'below') or caudal describes what is below, and nearer to the feet. Examples are the superior mediastinum, and inferior mediastinum. Neuroanatomy examples are the superior colliculus, and the inferior colliculus. In veterinary anatomy, the terms superior and inferior are not used except to describe the eye, eyelids, lips and inner ear, using instead dorsal and ventral.
=== Anterior and posterior ===
Anterior (from Latin ante 'before') describes what is in front, and posterior (from Latin post 'after') describes what is to the back of something. For example, for many fish the gill openings are posterior to the eyes and anterior to the tail. In veterinary anatomy, these terms are reserved for some structures of the head, instead using cranial and caudal throughout the rest of the body.